Electrophotographic systems and processes are known, including those described in U.S. Pat. Nos. 2,297,691; 3,666,363; 4,071,361, 5,489,498, 5,744,276, 5,942,366, and 6,002,895, the disclosures of which are incorporated herein by reference. In these systems and processes, in general, a photosensitive member, such as a photosensitive drum, is rotated through contact with a charging roller. An electrostatic latent image is formed on a photosensitive member comprising a photoconductive material, which image is then developed with a toner. The resultant toner image is transferred onto a transfer medium, such as paper, that is conveyed between the photosensitive member and an opposing transfer roller or belt. The toner image is then fixed on the transfer medium, such as by heating, pressing, or heating and pressing or with solvent vapor to obtain an imaged copy. Residual toner on the photosensitive member that has not been transferred is cleaned by various methods. The above steps may be repeated.
Components of these electrophotographic systems, such as the charging roller and transfer roller or belt and so forth, have been constructed with a central mandrel, in which a conductive elastic layer is formed at the outer periphery of the mandrel, such as described, for example, in U.S. Pat. No. 6,002,895, the disclosure of which is incorporated herein by reference. The electrical properties of the surface regions of these rollers can impact the performance and productivity of the systems using these components.
Accordingly, there remains a need for highly resistive coatings for electrophotographic systems having desired surface electrical properties, such as resistivity.